A charging/discharging circuit that controls charging/discharging of a secondary battery such as a lithium-ion secondary battery has a function of cutting off a current path flowing in the battery by operating a plurality of protective elements. More specifically, such a charging/discharging control circuit on/off-controls a current path flowing in a battery by using a switching transistor during a normal charging/discharging operation. However, since current value rises for a time longer than an operation time of the switching transistor when an instantaneous large current typified by a lightning surge is generated, a protective circuit such as a fuse that cuts off a current path is arranged in terms of excess-current protection. The charging/discharging circuit detects a condition of a battery, i.e., a voltage, a temperature, or the like to determine an abnormal state on the basis of the detection result, and on/off-controls a current path flowing in the battery by using a switching transistor or the like.
Patent Document 1 describes a protective circuit having a protective element that forcibly fuses a current path flowing in the battery in a noninvertible state when overcharge to the battery is detected, when the temperature of the battery abnormally increases, and when a switching element erroneously operates due to heat generation during charging of a secondary battery.